This invention relates to biochemical digestion of organic waste material and in particular to systems and methods suitable for compact toilets.
The broad principles of aerobic and anerobic digestion or sewage, organic factory waste and other organic matter dispersed in or dissolved in water have been recognized for many years. The removal of organic material is effected by the feeding and multiplication of microorganisms within the organic material. A typical sewage treatment system of the aerobic digestion type, usually referred to as an activated sludge process, consists in oversimplified form of an aeration stage and a settling stage. In the aeration stage raw sewage is aerated to promote rapid growth of microorganisms. The biochemical reactions which occur convert most of the organic material to volatile compounds, primarily carbon dioxide and water simultaneously with the formation of sludge. In practice the process is operated continuously, the raw sewage flowing into one end of an elongated aeration tank and along the length of the tank as a moving stream. A sludge-liquid mixture flows from the downstream end of the aeration tank to the settling stage which is simply a quiescent settling tank. After settling the sludge is withdrawn from the settling tank and a portion thereof is returned to the aeration tank to inoculate the incoming raw sewage with microorganisms and to thereby stimulate rapid synthesis of new organisms. The supernatant liquid, or effluent, is discharged to waste, usually after chlorination. Actual treatment plants are of course more complex than the above summary, although the principles of operation are the same.
While the principles of biochemical degredation of organic waste are well recognized, the biochemical processes themselves in an operating treatment plant of the above type are highly complex and are affected by any of several variables within the system. A properly operating system will produce rapidly settling sludge and a clear effluent substantially free of organics, but the system can rather rapidly become biochemically unbalanced in which case it can discharge pollution in the form of undigested waste, floating colonies of microorganisms and/or unsettled sludge.